This invention relates to a nickel based material for a semiconductor apparatus.
In the past, as a lead frame material for a semiconductor apparatus, an alloy with the common name "42 alloy"in which a principal component thereof is Fe-Ni having a composition of Fe 42% Ni and a copper alloy containing copper as a principal component have been used. The main properties required of a lead frame material are as follows: (i) a small coefficient of thermal expansion which is close to that of a silicon chip; (ii) superior heat dissipation capacity; (iii) high strength; (iv) superior workability; (v) superior corrosion resistance; and (vi) superior heat resistance. With regard to the above property (i), this is for preventing a silicon chip from cracking by stress therein which is caused by the difference in thermal expansion while heating at a die bonding process, in which the silicon chip which forms an electrical circuit is placed on the lead frame material. The above property (ii) is for preventing trouble in an integrated circuit (IC) arising from the self-exotherm of the IC during operation. And the above properties (iii) to (vi) are also both required for ever IC from a practical point.
The first reason why the above 42 alloy has been used in the main is that among the above required properties the coefficient of thermal expansion thereof is particularly small. Also, the 42 alloy is easy to compose during massproduction. Moreover, the 42 alloy has many merits, namely, the strength and workability thereof are superior, corrosion resistance and heat resistance are high, and adhesion to plastic packing is superior. However, the 42 alloy has defects in that it is costly and heat dissipation capacity thereof is inferior.
Therefore, copper alloys have been noted in recent years instead of the 42 alloy for their low cost and in that the copper alloy is a raw material having high electrical conductivity which will decrease the exotherm of the IC itself accompanied by an increased integration. The required properties of the copper alloy are approaching that of the 42 alloy within possible limits, however, the coefficient of thermal expansion, which is one of the most important properties, is large. This large coefficient of thermal expansion of the copper alloy must be compensated by IC production packaging techniques.